Hydraulic circuits for earth scraping machines



0d. 17, 1967 C. M. JOHNSON 3,

HYDRAULIC CIRCUITS FOR EARTH SCRAPING MACHINES Filed Jan. 14, 1965 6 Sheets-Sheet 1 np m g I NV EN TOR 6 /4/9155 jlfi/i/wvwxv ATTORNEY-S Ga. 17, 3967 c. M. JOHNSON HYDRAULIC CIRCUITS FOR EARTH SCRAPING MACHINES 6 Sheets-Sheet 3 Filed Jan. 14, 1965 r INVENTOR fi m-245s Mq/aUsWw/v' ATTORNEYS H:. %Ta LLL Um: H7, 3%? c. M. JOHNSON HYDRAULIC CIRCUITS FOR EARTH SCRAPING MACHINES 6 Sheets-Sheet 4 Filed Jan. 14, 1965 AililiJ IIIIL INVENTOR- [96 x156 flfv amvqs'o/v Oct. 17, 1967 c. M. JOHNSON HYDRAULIC CIRCUITS FOR EARTH SCRAPING MACHINES Filed Jan. 14, 1965 6 Sheets-Sheet 6 INVENTOR BY ,WM ATTORNEYs United States Patent 3,346,972 HYDRAULIC CIRCUITS FOR EARTH SCRAPING MACHINES Charies M. Johnson, Lubbock, Tex., assignor to Johnson Manufacturing Company, Lubbock, Tex., a corporation of Texas Filed Jan. 14, 1965, Ser. No. 425,433 3 Claims. (Cl. 37-8) ABSTRACT OF THE DISCLOSURE An earth scraping machine having a translatable bottom wall section, a translatable rear wall and an elevator mechanism in the bowl. The translatable walls, the elevator and the lift mechanism for the scraper are operated hydraulically. Special hydraulic circuits are provided for operating the translatable walls in proper sequence and for operating all the hydraulic elements of two scraping machines connected in tandem.

DISCLOSURE This invention relates to mobile earth scrapers and in particular to hydraulic control of the scraping and dumping mechanisms of such scrapers It is one object of the present invention to provide a hydraulic control circuit for operating the scraping and dumping mechanisms of tandem earth scrapers from a single, operator-manipulated control point.

It is another object to provide a hydraulic control circuit for an earth scraper having hydraulic jacks for adjusting the height of the front end of the scraper, an endless chain type conveyor powered by a hydraulic motor, a hydraulically retractable bottom wall which carries a mold board and a hydraulically movable rear wall for aiding in dumping.

It is a further object to provide a hydraulic control circuit for the above-mentioned type of scraper which hydraulically resists rearward movement of the retractable bottom Wall during a scraping operation.

It is yet another object to provide a hydraulic circuit for the above-mentioned type of scraper which automatically achieves a positive predetermined sequence of movement of the retractable bottom wall and the rear wall.

These and other objects and advantages will become apparent from the following detailed description in conjunction with the drawings in which:

FIGURE 1 is a side elevational view of tandem earth scrapers each of which has a hydraulic lift mechanism, conveyor, retractable bottom wall and movable rear wall;

FIGURE 2 is a fragmentary elevational view of the hydraulic rams for operating the bottom wall and rear wall of one of the scrapers of FIGURE 1;

FIGURE 3 is a schematic view of the hydraulic system for the tandem scrapers of FIGURE 1 wherein one fluid power source serves both scrapers;

FIGURE 4 is a schematic view of a modified hydraulic system for tandem scrapers wherein a separate fluid power source is provided for each scraper;

FIGURE 5 is a schematic view of a hydraulic system for a scraper showing a circuit which effects a hydraulic lock for a retractable bottom wall during a loading operation, thus eliminating the need for a mechanical lock for the bottom wall;

FIGURE 5A is a simplified schematic view of a hydraulic system for tandem scrapers showing another circuit which effects a hydraulic lock for a retractable bottom wall section;

FIGURE 6A is a simplified view of the system of FIGURE 5;

FIGURE 6B is a simplified view of a modification of the system of FIGURE 5;

FIGURE 7 is a fragmentary view of a sequence valve employed in the system of FIGURE 5; and

FIGURE 8 is a fragmentary view of a pilot-operated check valve employed in the system of FIGURE 5.

Referring to FIGURE 1 there is shown a pair of twowheel earth scrapers 10 and 10' arranged in tandem relationship behind a single tractor 12 whose wheels are indicated at 14.

The leading scraper is drawn by the tractor 12 through a draft connection 16 of the universal type, and the trailing scraper 10' is connected to the rear end of the leading scraper 10 by means of a similar coupling 16'.

The scrapers are identical and, as shown, are of the general type described in Johnson et al. application Ser. No. 279,987 filed May 13, 1963, now Patent No. 3,274,- 711. A brief description of the leading scraper 1G with primed reference numerals being applied to the corresponding parts of the trailing scraper 10 will be sulficient for an understanding of the present invention. Broadly, the leading scraper 10 includes an open-top, open-front, dirt carrying container 18 having a longitudinally movable back wall 20 and a bottom wall which is formed of a fixed rear section 22 and a longitudinally movable section 24 positioned forwardly of and slightly below the fixed section 22. A downwardly and forwardly extending dirt-digging scraper blade 26 is secured to the forward edge of the movable bottom section 24. The rear end of the container 18 is provided with a transverse axle 28 on which a pair of laterally spaced, ground engaging wheels 30 are journaled. The container 18 is connected to the tractor 12 by means of a Y-shaped beam structure having a pair of laterally spaced arms 36) which straddle the forward part of the container, and which are pivoted at their rear ends to the outside of the container at 32. Forwardly of the container the arms converge to form a gooseneck structure 34 which terminates at the universal type coupling 16.

The container 18 is pivoted about its axle in a vertical plane by means of a pair of generally vertical, laterallyspaced, double-acting hydraulic cylinders 36 or rams. The upper ends of the lift cylinders are pivoted at 38 to the gooseneck structure, and the lower end of the piston rods are pivoted at 40 to upstanding ears on each side of the front of the container 18.

The lateral extremities of the movable bottom section 24 are suepended from the sides of the container 18 by means of rollers 42 carried on longitudinally spaced bracket 44 extendin upwardly from the bottom section 24. The rollers 42 on each side of the machine are movable along upper and lower longitudinal rails 46, 48 which are secured to the side of the container 18. The rails 46, 48 extend rearwardly a sufficient distance to permit the movable bottom section 24 to move completely under the fixed bottom section 22. The front end of the movable section 24 is provided on each side with a laterally extending pin 50 which fits in a slot in a bracket to restrain vertical movement of the section 24 when in the forward position. The rear end of the section 24 is provided on each side with an elongated arm 54 which is pivoted at its forward end to the section at 56 and at its rear end to an upwardly extending link 58 at 60. The upper end of the links are pivoted to the frame of the scraper at 62 for movement in a vertical plane.

It will be seen that rearward movement of the lower ends of the links 58 will pull the movable bottom section 24 rearwardly. To effect this movement and movement in a forward direction, a generally horizontal double-acting hydraulic cylinder 64 or ram is associated with each link. As seen in FIGURE 2, the cylinders 64 are located behind the links 58 with their rear ends pivoted to the scraper frame at 66 and the forward ends of the piston rods pivoted at 68 to a releasable latch mechanism associated .with the links 58 and the arms- 54. In the position shown in FIGURE 2 the movable bottom section 24 is in its forward position and is restrained against rearward movement by a pair of vertically movable latch members 70, one of which is hooked over the rear end of each arm 54. The latches are pivoted to the scraper frame at 72 for movement in a vertical plane and are disengaged from the arms 54 immediately upon retraction of the cylinders 64. This release function is achieved by means of a finger 74 which is pivoted at 76 intermediate its ends to each of the links 58. The upper ends of the fingers 74 connect with the cylinders 64 at the pivots 68. The lower end of the fingers 74 have hooked-shaped protuberances which engage a curved cam surface on theupper rear edges of the latches 70 so that initial retraction of the cylinders 64 raises the lower ends of the latches 70 away from the ends of the arms 54. Continued retraction of the cylinders 64 swings the links 58 rearwardly, bringing with them the arms 54 and the movable bottom section 24. i

Still referring to FIGURE 2 it will be seen that the movable rear-wall 20 of the container 18 is power driven forwardly and rearwardly by means of a horizontally mounted double-acting hydraulic cylinder 78 or ram psitioned along the longitudinal axis of the scraper. The rear end of'the cylinder is pivoted at 80 to the scraper frame and the forward end of its piston rod is pivoted at 82 to a bracket on the lower back side of the rear wall 20. During movement, the rear wall 20 is guided by longitudinal tracks carried by the scraper frame at vertically spaced locations and by track-engaging rollers carried by the wall.

An endless chain, scraper-type conveyor 84 is mounted between the sides of the container 18 in a rearwardly and upwardly inclined position. The conveyor 84 includes a pair of transversely spaced, elongated frame members 86 carrying suitable sprockets and rollers over which a pair of endless chains 88 are looped. Extending transversely between the chains and connected thereto are rigid flights 90 which drag earth rearwardly into the container 18 when the chains 88 are run in a counterclockwise direction as viewed in the drawing. A reversible hydraulic motor 92 is secured to the conveyor frame 86 for driving the conveyor 84. Conveniently, the motor 92 is mounted on the upper end of the frame 86 with its rotating output shaft coaxial with and drivingly connected with one of the sprockets. Preferably, the conveyor 84 is pivotally mounted within thecontainer 18 so that its lower end can ride up on the incoming dirt during a loading operation. The pivoted mounting includes a transverse rod 94 secured to the conveyor frame members and journaled at its ends in links 96 which are themselves pivotally connected at their lower ends to the sides of the container 18. Further details of suitable conveyor mountings may be found in Patent No. 2,984,022 andin application Ser. No. 257,277 filed Feb. 8, 1963.

During an earth scraping or loading operation the scrapers and 10 are towed forwardly by the tractor 12 and the front ends of the dirt containers 18, 18' are loweredby extension of the lift cylinders 36, 36 until the blades 26, 26' dig into the ground to a desired depth. Loosened dirt passing over the blades 26, 26' is engaged by the lower flights 90, 90 of the conveyors 84, 84 and is thereby urged rearwardly into the containers 18, 18"

by operating the conveyors 84, 84' in a counter-clockwise direction as viewed in FIGURE 1. To discharge a load of dirt, the front ends of the containers 18, 18 are raised, and the movably bottom sections 24, 24 are slowly moved rearwardly by the retract cylinders 64,,

64' while the tractor 12 tows the scrapers forwardly. At the time, or prior to retraction of the bottom sections 24, 24', the conveyors 84, 84 may be operated in the opposite direction, if desired. When the bottom sections 24, 24 reach their fully retracted positions,,the rear walls 20, 20' are slowly moved forward by cylinders 78, 78 to push the remainder. of the dirt from the container.

Referring to FIGURE 3, there is shown schematically the power source and hydraulic circuits and their controls for operating the tandem scrapers 10, 10' of FIG- URE 1. The power source, which is carried by the tractor, includes two distinct hydraulic circuits, each with its own pump and exhaust or low pressure line. One pump 98 powers the conveyor motors 92, 92' and the other pump 100 powers the lift cylinders 36, 36', bottom section or retract cylinders 64, 64' and rear wall of eject cylinders 78, 78'. Both pumps draw from a common hydraulic fluid supply which includes a filter 102 and a reservoir 104. The pumps are driven by the tractor engine and are provided with flexible hydraulic lines for transmitting pressurized fluid to the driven components. In the i the electrical system of the tractor.

The hydraulic circuit for the conveyor motors 92, .92 includes a flexible pressure line 106 leading from the pump 98 to valve No. 1 carried by the leading scraper 10 and through line 122 to valve No. 2 carried by scraper 10" from which a return line 108 leads to the reservoir 104. Each of valves No. 1 and No. 2 are three-position, four-connection, open-center spool valves of known construction. They are series-connected spring-centered and have a solenoid plunger attached to each end of the spool to move the same in either direction upon manual throwing of the respective switch at the console 105. Electrical.

leads 110, 112 and 114, 116 are provided from the console to valves Nos. 1 and 2, respectively.

In the position shown in FIGURE 3 hydraulic fluid is flowing through the line 106 from the pump 98 to valve No. 1, through a line 118 to the conveyor motor 92, back to valve No. 1 through line 120, then to valve No. 2 by way of a line 122. Flow is then through the conveyor motor .92 in a similar manner by way of lines 124 and 126 and then back to the reservoir through the exhaust line 108. Reverse operation of either conveyor motor is achieved by throwing its respective switch in the opposite direction to move the spool of the respective valve in the opposite direction. Since. the exhaust port of valve No. 1 is connected to the inlet port of valve No. 2 by the line 122 the movement of the spool of either valve does not affect the direction of fluid flow to the other valve.

When either conveyor switch is placed in an open or neutral position, the spool of the respective valve becomes centered by its centering springs, and the pressurized fluid flows through the open center of the respective valve to exhaust and does not drive the motor. In the case of valve No. 1 the fluid fiows directly to valve No. 2 and if that valve is also centered, the fluid then flows directly to the exhaust line 108 and thence to the reservoir 104. When the valves are centered, equal pressure is transmitted to the inlets and outlets of the motors 92, 92' with the result that the conveyors 84, 84 either stand still or move under the forces transmitted to them by movement of the load of dirt in the containers 18, 18.

The hydraulic circuit for the lift cylinders 36, 36', the

rear wall cylinders 78, 78' and the bottom section cylinders 64, 64' includes four series-connected spool valves of the open-center type, two of which (valves No. 3 and No. 5) control the lift cylinders and two of which (valves No. 6 and No. 4) control the cylinders associated with the rear wall and the bottom section. These valves, like valves No. 1 and No. 2, are three-position, four-connection spring-centered and solenoid-operated from separate double-pole, double-throw switches in the console 105. The valves are connected in the order No. 3, No. 5, No. 6 and No. 4 with a pressure line 128 leading from the pump 100 to the inlet of valve No. 3 and the exhaust port of each valve being connected to the inlet of the next valve by an appropriate line 130, 132 and 134. The exhaust port of valve No. 4 is connected to the reservoir 104 by line 136. Valves Nos. 3 and 4 are carried on the leading scraper and valves Nos. 5 and 6 are carried on the trailing scraper 10'.

' More specifically, valves Nos. 3, 5, 6 and 4 are of the open-center type in which the spool, when centered, blocks the ports to the work cylinder while passing the pressurized fluid to its exhaust port. That is, when the spool of valve No. 3 is centered, its work ports which are connected to lines 138 and 140 are blocked so that the parallel-connected lift cylinders 36 of the leading scraper 10 will not move. At the same time, the exhaust line 130 supplies pressurized fluid to valve No. 5 so that it may be operated independently of valve No. 3. Similarly, valve No. 5, when centered, permits of fluid pressure to valve No. 6 through the line 132. The latter valve permits flow of fiuid to valve N0. 4 in the same manner through the line 134.

Valve No. 4 has its work ports connected by means of lines 142 and 144 to the pair of bottom section cylinders 64 and to the rear Wall cylinders 78. Each line leads to a conventional sequence valve 146 or 148, which during a dumping operation, directs the pressurized fluid first to the bottom wall cylinders 64 to retract them and then to the rear wall cylinder 78 to extend it. Thus, the bottom wall section will be fully retracted before the rear wall begins to move forward. At the end of a dumping operation, the operator throws the appropriate switch at the console 105 to reverse the flow of pressurized fluid from the work ports of valve No. 4. The sequence valves 146 and 148 effect a positive retraction of the rear wall before the bottom wall section moves forward. It has been found that the above-described sequential action during and after a dumping operation results in more efficient use of the scraping machine. The desired sequential operation can also be effected with a single sequence valve associated with valve No. 4. For example, sequence valve 146 may be omitted and the line 154 connected to lines 144 and 152. As is known in the art, a sequence valve is essentially an on-otf valve which is included in a hydraulic circuit when it is desired to interlock two cylinders so that when one cylinder has finished its stroke the attendant pressure rise causes the valve to open and admit pressure to the other cylinder.

Referring more specifically to the connections of the cylinders 64 and 78, as shown in FIGURE 3, it will be seen that these cylinders are connected in parallel with the rear wall cylinder 78 arranged to move in the opposite direction from the others. Thus, the working line 144 is connected through its sequence valve 146 to the outer side of the pistons in the bottom section cylinders 64 by 1 means of lines 150 and 152, and to the inner side of the piston in the rear wall cylinder 78 by means of line 154. The other working line 142 is connected through its sequence valve 148 to the inner side of the pistons in cylinders 64 by means of lines 156 and 158 and to the outer side of the piston in cylinder 78 by means of line 160.

Referring to FIGURE 4 there is shown a modified hydraulic circuit for tandem scrapers in which an auxiliary and distinct power source, Power Source No. 2, is

carried by the trailing scraper 10 for operating the motor and cylinders of that scraper. The valves and operation of the cylinders in this arrangement are the same as those of FIGURE 3, the primary difference being that there are no hydraulic connections between the two scrapers.

The hydraulic circuit for the leading scraper 10 of the modified tandem arrangement differs from the leading scraper arrangement of FIGURE 3 only in two minor respects. First, in FIGURE 4 the pressurized fluid from the motor control valve, valve No. 1A, flows directly back to the reservoir 104 of Power Source No. 1 through a line rather than continuing on to the conveyor on the trailing scraper 10'. Second, the pressurized fluid from the valve controlling the lift cylinders 36 of the leading scraper, valve No. 3A, is passed by a line 172 to valve No. 2A which controls the bottom section cylinders 64 and the rear wall cylinder 78 of the same scraper. This is in contrast to the FIGURE 3 construction in which the pressurized fluid travels from valve No. 3 on the leading scraper 10 to valve No. 5 on the trailing scraper 10' by way of line 130.

The hydraulic circuits for the trailing scraper 10 of FIGURE 4 are duplicates of the circuits for the leading scraper 10. The conveyor motor 92' and the various cylinders are supplied with pressurized fluid from Power Source No. 2 which includes a separate engine 166 for driving a pair of hydraulic pumps 162, 164. The engine 166 may be an internal combustion engine carried by the trailing scraper 10'. As before, one pump provides pressurized fluid for the conveyor motor and the other provides pressurized fluid for the various cylinders. A single console 168 of six electrical switches controls the position of the valves on both scapers, as in FIGURE 3.

FIGURE 5 shows another arrangement by which a hydraulic conveyor motor and the hydraulic cylinders of a scraper may be operated and controlled. The arrangement is shown as applied to a single scraper, but it will be understood that the arrangement can be modified or duplicated so as to be applied to tandem scrapers. The FIGURE 5 system contemplates a scraper having a hydraulic conveyor motor, lift cylinders, bottom wall cylinders and rear wall cylinder, all as described with respect to FIGURE 1, except that no mechanical latch is provided for the movable bottom wall section. The hydraulic characteristics of the system differ from those previously described in that a hydraulic lock is effected for restraining rearward movement of the movable bottom section during a loading operation thus eliminating the need for a mechanical latch. In addition, positive sequence control of the dump cycle is achieved in a different manner.

As shown in FIGURE 5 there are again two distinct hydraulic circuits, one for powering a hydraulic motor for a conveyor and one for powering a pair of lift cylinders 176, a pair of bottom section cylinders 178 and a rear wall cylinder 180. The power source includes a reservoir 182 common to both circuits and two hydraulic pumps 184 and 186 driven by the tractor engine. The output of the pump 184 is connected by means of a line 188 to a valve C whose work ports are connected to the inlet and outlet of the hydraulic motor 174 by lines 190 and 192. The exhaust port of the valve is connected by a line 194 with a common return line 196 which leads to the reservoir 182 through a filter 198.

Valve C is a three-position, four-connection, opencenter spool valve of known construction. When the spool is centered, high pressure fluid is routed directly to the exhaust line 194 so that no power is transmitted t6 the motor. At the same time the valve places the work ports in communication with each other so that the motor 174 either remains still or turns as a result of forces trans mitted to the conveyor by the movement of the load of dirt.

The output of the pump 186 connects by means of a line 20 to the inlet control port of valve A whose work 7 ports are connected to the lift cylinders 176. One work port connects directly with the outer ends of the lift cylinders by means of a line 202, and the other work port connects by way of a line 204 to a line 206 which leads to the bottom section cylinders 178 and the rear wall cylinder 180. The exhaust port of valve A connects by means of a line 208 with one of the control ports of a valve B. The other control port of the latter communicates with the common return line 196 by way of a line 210. One work port of valve B communicates with the line 204 by way of a line 212 and the other work port leads to the cylinders 178 and 180 by means of a line 214.

Valves A and B are three-position, four-connection closed-center spool valves of known construction. When the spool of one of these valves is centered, the work ports of that valve are blocked so that the work cylinder whose opposite ends are connected to the work ports is locked against movement in either direction. At the same time, the control ports of the valve are in communication with each other so that fluid delivered to either of these ports is passed directly to the other control port wihout change in pressure.

The circuit for the bottom section cylinders 178 includes work lines 216, 218 and 220,222 connected to the.

inner and outer ends, respectively, of the cylinders. The outer end lines 220, 222 of the cylinders connect with the line 214 from valve B and the inner lines 216, 218 connect with the line 206 by way of a valve D.

As shown in FIGURE 8 valve D is a pilot-operated check valve of known construction having two flow ports connected between the line 206 and the line 218 by means of lines 224 and 226. A spool 228 within the housing of the valve has its opposite ends exposed to the pressure in the return line 214 and the pressure in the exhaust line 196. The spool is longitudinally movable between one position in which the flow ports are blocked and another position in which the flow ports are in communication with each other.

The rear wall cylinder 180 is provided with work lines 230 and 232, the former connecting with the line 206, and the latter connecting with line 214 through a valve E. Valve E is a sequence valve of known construction which, during a dumping operation, direct the pressurized fluid first to the bottom wall cylinders 178 to retract them and then to the rear wall cylinder 180 to extend it. As seen in FIGURE 7 the valve housing has two work ports, one of which is connected to the line 214, and the other of which connects with the line 232 by means of a line 234. A spool 236 is movable between one position in which it blocks the work ports and another position in which it permits flow through the valve. One end of the spool is exposed to the pressure in the line 214 and the other end is exposed to pressure of the line 196. A bypass line 238 containing a check valve .240 connects the line 214 with the line 232.

Movement of the spools of the valves A, B and C may be effected in any convenient manner as by means of a manually operated lever (not shown) connected with an end of each spool.

The arrangement of FIGURE differs from the arrangement of FIGURES 1 and 4 also in that one less hydraulic line is employed in the FIGURE 5 arrangement. Specifically the latter provides a common line from valve A to both lift circuit and the dump circuit whereas the former employs independent lines from the valve to the circuits. This difference will be apparent from comparison of the simplified circuits illustrated in FIGURES 6A and 6B wherein only the spool valves, one lift cylinder and the rear wall cylinder are shown. FIGURE 6A illustrates the basic hydraulic lines employed in the circuits shown in detail in FIGURE 4, and FIGURE 6B illustrates the basic lines employed in the FIGURE 5 arrangement. In both FIGURES 6A and 6B the hydraulic lines and other components which would be the same in both systems have been omitted in the interest of clarity.

8 It will beunderstood that theindependent-line feature of FIGURES 3 and 4 may be employed, if desired, in the FIGURE 5 arrangement without any change except in the connections of the hydraulic lines. That is, the particular valve components of the different systems do not limit the systems to the precise connections which have been illustrated.

The operation of the scrapers of FIGURE 1 by means of the hydraulic circuits of FIGURES 3 and 4 has been described in the description of the components of those systems. The operation of theFIGURE 5 arrangement achieves the same movements of the front end of the container, the conveyor, and the movable bottom and rear walls. The details of the operation of the FIGURE 5 arrangement will be apparent from the following series of steps which cover a complete cycle from loading to dumping.

Step 1.L0ading operation Conveyor system-Valve C is opened to allow fluid to flow from the reservoir 182 through the pump 184 through valve C to cause the motor 174 .to operate the conveyor in a forward direction. Return fluid is routed through valve C through the filter 198 to the reservoir 182.

Container lift system.Valve A is opened to allow fluid.

to flow from the reservoir 182 through the pump 186 through the valve A to the top of the lift cylinders 176 to cause the front end of the container to be lowered to a desired depth. Valve A is then centered to block fluid flow to and from the cylinders 176 thereby holding the container at the desired level. Fluid displaced from the bottom of the lift cylinders 176 is routed through the line 202, through the open side of valve A and through lines 208,1

210 and 196 to the reservoir 182.

Dump system.--Valve B is in its center position andthereby locks the bottom section cylinders 178 and the rear wall cylinder 180 by preventing fluid flow to and from these cylinders.

Step 2.Raising container and reversing conveyor Conveyor system-Valve C is moved to opposite open position to reverse the cycle described in Step 1.

Container lift system.--Valve A is opened in opposite direction to allow flow of fluid from the pump 186 through Step 3.-Beginning of dumping operation Conveyor system.Valve C is centered to allow cir culation of fluid on either side of valve C but no passage through valve C to prevent transmittal of power to motor and to allow the conveyor to either stand still or to move with the forces transmitted to it from the substance being pumped from the container.

Container lift syuvem.Valve A is centered to effect a complete block of fluid through this system.

Dump system-Valve B is opened to allow fluid to flow from reservoir 182 througth pump 186 through valve A, line 208, valve B to line 214 and thence to the front end of cylinders 178 allowing the bottom section to ,be moved in a rearward direction. The fluid displaced from the rear of the Cylinders 178 is routed by way of line 226 through valve D, which has been opened by its pilot line from the front end of cylinders, thus allowing return fluid to be routed through the common line 206 through valve B, lines 210 and 196.

Step 4.Remainder of dumping operation Conveyor system.(Same as Step 3.)

Container lift sysiem.-(Same as Step 3.)

Dump system.Valve B is in the same position as in Step 3. The cylinders 178 have reached the end of their travel in a rearward direction allowing a pressure buildup at valve E suflicient to overcome a predetermined setting at valve E allowing fluid to pass through valve E to the rear of cylinder 180. This causes the rear wall to move in a forward direction while the fluid displaced from the front of cylinder 18!) is routed through the common line 206 through the open side of valve B to lines 210' and 196.

Step 5.-Rear will return Conveyor system.-(Same as Step 3.)

Container lift system-(Same as Step 3.)

Dump system.--Valve B is opened to allow fluid to pass from reservoir 182 through pump 186, line 200, valve A, line 208, valve B, line 206 to the forward end of cylinder 180 causing the rear wall to move rearwardly to its original position. The fluid displaced from the rear of cylinder 180 is routed through the bypass 240, 238 of valve E through line 214, through the open side of valve B to lines 210 and 196.

Step 6.Bottom door close Conveyor sys!em.(Same as Step 3.)

Container lift system.(Same as Step 3.)

Dump system.--Valve B is held in the same position as in Step 5. The cylinder 180 has reached the end of its rearward travel thus allowing pressure to build up to overcome the predetermined pressure on the return side of valve D allowing fluid to pass to the rear side of cylinders 178 through lines 206, 224, 226. This causes the bottom section to move to its forward position while permitting the fluid displaced from the front side of cylinders 178 to flow through line 214, the open side of valve B and into lines 210 and 196.

Referring to FIGURE A there is shown another hydraulic circuit for effecting a hydraulic lock on the cylinders employed to operate a retractable bottom wall section. The illustrated system includes many of the same elements as the system of FIGURE 3, and FIGURE 3 reference numerals together with the letter a are employed to designate elements which are the same in structure and function in the two figures. For simplicity, the portions of the circuit of FIGURE 5A which are identical with portions of the FIGURE 3 circuit are omitted in FIGURE 5A.

As shown, the FIGURE 5A circuit is applied to a tandem arrangement of scrapers for which a single fluid power source is provided. The source includes a reservoir 104a, filter 102a and two engine-driven pumps 98a and 100a. The pump 98a supplies pressurized fluid to the conveyor motors (not shown) of both scrapers through a line 106a. The fluid from this portion of the circuit returns to the reservoir through the line 108a. The pump 100a supplies pressurized fluid to a line 128a for sequential transmittance to the lift and dump cylinders of both scrapers, the fluid ultimately returning to the reservoir through the line 136a.

The construction and operation of the valves Nos. 3, 4, 5 and 6 employed in the lift and dump portions of the FIGURE 5A circuit has been described in connection with FIGURE 3 and will not be repeated. The novel aspects of FIGURE 5A pertain to the connection of valves No. 4 and No. 6 to their respective hydraulic cylinders so as to effect a predetermined sequential action and to lock the bottom wall cylinder in an extended position (bottom wall section forward) during a scraping operation. For this purpose a description of that portion of the circuit associated with valve No. 4 will suflice, this valve being actuated from a control panel (not shown) for controlling the dump cylinders on scraper No. 1. An identical arrangement (not shown) is provided for controlling the dump cylinders on scraper No. 2.

The dump mechanism associated with valve No. 4 includes, as before, a pair of bottom wall cylinders 64a and a rear wall cylinder 78a, the former being extensible to move the bottom wall section of scraper No. 1 forward and the latter being extensible to move the rear wall forward. The valve receives pressurized fluid through the line 134a from scraper No. 2 and exhausts fluid to the line 136a. One work port of the valve connects by way of a line 144a to a check valve 244. A line 246 connects the extend sides of the bottom wall cylinders 64a to the check valve 244, and a line 248 connects the retract side of the rear wall cylinder 78a to the check valve 244. The other work port of valve No. 4 connects with the extend side of the rear wall cylinder 78a by way of a line 250 and with the retract sides of the bottom wall cylinders 64a by way of a line 252. The line 250 incorporates a sequence valve 254 which is arranged to fully retract the bottom wall cylinders .before extending the rear wall cylinder 78 during a dumping operation. Similarly the sequence valve 254 retracts the rear wall cylinder 78a before extending the bottom wall cylinders 64a after the completion of a dumping operation. After the bottom wall cylinders have been extended to move the bottom wall section to its full forward position, the check valve 244 blocks the flow of fluid through the line 246 thus preventing rearward movement of the bottom wall section during a scraping operation.

While specific embodiments of the present invention have been described in detail, modifications will occur to those skilled in the art and it is not intended that the invention be limited to the described details except as they appear in the appended claims.

What is claimed is:

1. An earth scraping machine comprising: a mobile dirt-carrying container having upright side walls, a longitudinally movable rear wall and a longitudinally movable bottom wall section at the front of said container, said section carrying a downwardly extending dirt-scraping blade at its forward edge; an endless scraper-type conveyor mounted in said container between said side walls; bydraulic ram means for raising and lowering the front end of said container with respect to the ground; hydraulic ram means for moving said rear Wall forwardly and rearwardly; hydraulic ram means for moving said bottom wall section forwardly and rearwardly; rotary hydraulic motor means for operating said conveyor; a power source including two hydraulic pumps and a reservoir of hydraulic fluid; a first hydraulic circuit including conduit means connecting one of said pumps with said motor and a motor flow control valve for controlling the flow of hydraulic fluid in said circuit; a second hydraulic circuit separate from said first circuit and including conduit means connecting the other of said pumps with the hydraulic ram means associated with the front end of said container, said bottom wall section and said rear wall, said second circuit including a lift flow control valve associated with the ram means for moving the front end of the container; a dump flow control valve associated with the ram means for operating the bottom wall section and rear wall; means associated with said dump valve for sequentially operating the last-named ram means; and a trailing scraping machine mechanically coupled to and of the same construction as said first-named scraping machine, said trailing machine having hydraulic ram means for raising and lowering its front end, hydraulic ram means for moving its rear wall, hydraulic ram means for moving its bottom wall section and rotary hydraulic motor means for operating its conveyor and wherein said motor, lift and dump flow control valves are threeposition, four-connection spool valves each having two control ports and two work ports, said first hydraulic circuit including a second motor flow control valve connected in series with said first-named motor flow control valve, said second hydraulic circuit including a second lift valve in series with said first-mentioned lift valve,

1 1 a second dump valve in series with said second lift valve, said first-mentioned dump valve being in series with said second dump valve.

2. Apparatus as in claim 1 wherein said means for sequentially operating the ram means associated with the bottom wall section and the rear wall includes a sequence valve connected betwen said dump flow control valve and said last-mentioned ram means.

3. Apparatus as in claim 1 wherein said dump flow 12 includes conduits connecting said last-named ram means in parallel with said work ports.

References Cited UNITED STATES PATENTS 2,778,378 1/1957 Presnell 91-412 X 3,210,869 10/1965 Hein 37-8 3,258,926 7/1966 Junck et al 378 X control valve has a pair of work ports and wherem said 10 ABRAHAM G STONE, Primal? Examinermeans for sequentially operating the ram means associated with the bottom wall section and the rear wall A. E. KOPECKI, Assistant Examiner. 

1. AN EARTH SCRAPING MACHINE COMPRISING: A MOBILE DIRT-CARRYING CONTAINER HAVING UPRIGHT SIDE WALLS, A LONGITUDINALLY MOVABLE REAR WALL AND A LONGITUDINALLY MOVABLE BOTTOM WALL SECTION AT THE FRONT OF SAID CONTAINER, SAID SECTION CARRYING A DOWNWARDLY EXTENDING DIRT-SCRAPING BLADE AT ITS FORWARD EDGE; AN ENDLESS SCRAPER-TYPE CONVEYOR MOUNTED IN SAID CONTAINER BETWEEN SAID SIDE WALLS; HYDRAULIC RAM MEANS FOR RAISING AND LOWERING THE FRONT END OF SAID CONTAINER WITH RESPECT TO THE GROUND; HYDRAULIC RAM MEANS FOR MOVING SAID REAR WALL FORWARDLY AND REARWARDLY; HYDRAULIC RAM MEANS FOR MOVING SAID BOTTOM WALL SECTION FORWARDLY AND REARWARDLY; ROTARY HYDRAULIC MOTOR MEANS FOR OPERATING SAID CONVEYOR; A POWER SOURCE INCLUDING TWO HYDRAULIC PUMPS AND A RESERVOIR OF HYDRAULIC FLUID; A FIRST HYDRAULIC CIRCUIT INCLUDING CONDUIT MEANS CONNECTING ONE OF SAID PUMPS WITH SAID MOTOR AND A MOTOR FLOW CONTROL VALVE FOR CONTROLLING THE FLOW OF HYDRAULIC FLUID IN SAID CIRCUIT; A SECOND HYDRAULIC CIRCUIT SEPARATE FROM SAID FIRST CIRCUIT AND INCLUDING CONDUIT MEANS CONNECTING THE OTHER OF SAID PUMPS WITH THE HYDRAULIC RAM MEANS ASSOCIATED WITH THE FRONT END OF SAID CONTAINER, SAID BOTTOM WALL SECTION AND SAID REAR WALL, SAID SECOND CIRCUIT INCLUDING A LIFT FLOW CONTROL VALVE ASSOCIATED WITH THE RAM MEANS FOR MOVING THE FRONT END OF THE CONTAINER; A DUMP FLOW CONTROL VALVE ASSOCIATED WITH THE RAM MEANS FOR OPERATING THE BOTTOM WALL SECTION AND REAR WALL; MEANS ASSOCIATED WITH SAID DUMP VALVE FOR SEQUENTIALLY OPERATING THE LAST-NAMED RAM MEANS; AND A TRAILING SCRAPPING MACHINE MECHANICALLY COUPLED TO AND OF THE SAME CONSTRUCTION AS SAID FIRST-NAMED SCRAPING MACHINE, SAID TRAILING MACHINE HAVING HYDRAULIC RAM MEANS FOR RAISING AND LOWERING ITS FRONT END, HYDRAULIC RAM MEANS FOR MOVING ITS REAR WALL, HYDRAULIC RAM MEANS FOR MOVING ITS BOTTOM WALL SECTION AND ROTARY HYDRAULIC MOTOR MEANS FOR OPERATING ITS CONVEYOR AND WHEREIN SAID MOTOR LIFT AND DUMP FLOW CONTROL VALVES ARE THEREPOSITION, FOUR-CONNECTION SPOOL VALVES EACH HAVING TWO CONTROL PORTS AND TWO WORK PORTS, SAID FIRST HYDRAULIC CIRCUIT INCLUDING A SECOND MOTOR FLOW CONTROL VALVE CONNECTED IN SERIES WITH SAID FIRST-NAMED MOTOR FLOW CONTROL VALVE, SAID SECOND HYDRAULIC CIRCUIT INCLUDING A SECOND LIFT VALVE IN SERIES WITH SAID FIRST-MENTIONED LIFT VALVE, A SECOND DUMP VALVE IN SERIES WITH SAID SECOND LIFT VALVE, SAID FIRST-MENTIONED DUMP VALVE BEING IN SERIES WITH SAID SECOND DUMP VALVE. 